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From: Winfield Hill on 11 Jun 2010 19:15
John Fields wrote...
>
> On Fri, 11 Jun 2010 07:02:03 -0500, John Fields wrote:
>> On 10 Jun 2010 13:23:55 -0700, Winfield Hill wrote:
>>
>>> In a ringing bell application, as the supply voltage sags,
>>> and the amplitude drops, I imagine the circuit will move
>>> from class C back to class A operation, before stopping.
>>
>> Why imagine?
>>
>> Here's a circuit list that'll show it all _and_ it'll create
>> a .wav file, "bong.wav" in whatever folder the cicuit's in,
>> so you can hear it.
>>
>> Enjoy! :-)
> Oops... Here it is: [ big snip ]

Thanks, John. I like the bong! But it's a little
on the long side tho, don'cha think? That's one
problem with perfect inductors and capacitors, too
high Q. How about adding some esr loss for the
inductor, or a parallel resistor on the LC tank?

I wonder, don't we need a bypass capacitor on Q2,
the oscillator-supply voltage emitter follower?
Check out the waveform there. And of course,
then we'll need a Q2 base resistor to help stop
the RF oscillation thing - you know, the old
emitter-follower with cap load, etc.


--
Thanks,
- Win
From: John Fields on 13 Jun 2010 14:29
On 11 Jun 2010 16:15:45 -0700, Winfield Hill
<Winfield_member(a)newsguy.com> wrote:

>John Fields wrote...
>>
>> On Fri, 11 Jun 2010 07:02:03 -0500, John Fields wrote:
>>> On 10 Jun 2010 13:23:55 -0700, Winfield Hill wrote:
>>>
>>>> In a ringing bell application, as the supply voltage sags,
>>>> and the amplitude drops, I imagine the circuit will move
>>>> from class C back to class A operation, before stopping.
>>>
>>> Why imagine?
>>>
>>> Here's a circuit list that'll show it all _and_ it'll create
>>> a .wav file, "bong.wav" in whatever folder the cicuit's in,
>>> so you can hear it.
>>>
>>> Enjoy! :-)
>> Oops... Here it is: [ big snip ]
>
> Thanks, John. I like the bong! But it's a little
> on the long side tho, don'cha think? That's one
> problem with perfect inductors and capacitors, too
> high Q. How about adding some esr loss for the
> inductor, or a parallel resistor on the LC tank?

---
Sorry for the delay...

Better yet, I chose a real-world inductor, included the specified
parasitic R, and added, arbitrarily, an ohm as the ESR for the cap
since I was too lazy to go shopping for that.
---

> I wonder, don't we need a bypass capacitor on Q2,
> the oscillator-supply voltage emitter follower?

---
It doesn't seem to affect the operation of the oscillator, and it's
just another part if it's not needed.
---

> Check out the waveform there. And of course,
> then we'll need a Q2 base resistor to help stop
> the RF oscillation thing - you know, the old
> emitter-follower with cap load, etc.

---
But, since no emitter-follower cap load, no base resistor. ;)

Here's the circuit, oscillating at around 675Hz.

Sounds pretty good, I think, and the bong doesn't last as long as it
used to.

Version 4
SHEET 1 936 680
WIRE -864 48 -1072 48
WIRE -800 48 -864 48
WIRE -576 48 -704 48
WIRE -448 48 -576 48
WIRE -352 48 -448 48
WIRE -448 64 -448 48
WIRE -352 64 -352 48
WIRE -864 96 -864 48
WIRE -576 96 -576 48
WIRE -928 144 -976 144
WIRE -448 160 -448 128
WIRE -352 160 -352 144
WIRE -352 160 -448 160
WIRE -976 176 -976 144
WIRE -1072 192 -1072 48
WIRE -752 192 -752 112
WIRE -752 192 -864 192
WIRE -448 192 -448 160
WIRE -576 240 -576 176
WIRE -512 240 -576 240
WIRE -864 272 -864 192
WIRE -752 272 -752 192
WIRE -976 288 -976 256
WIRE -576 304 -576 240
WIRE -448 320 -448 288
WIRE -352 320 -448 320
WIRE -448 336 -448 320
WIRE -352 336 -352 320
WIRE -1072 432 -1072 272
WIRE -976 432 -976 368
WIRE -976 432 -1072 432
WIRE -864 432 -864 352
WIRE -864 432 -976 432
WIRE -752 432 -752 336
WIRE -752 432 -864 432
WIRE -576 432 -576 368
WIRE -576 432 -752 432
WIRE -448 432 -448 416
WIRE -448 432 -576 432
WIRE -352 432 -352 416
WIRE -352 432 -448 432
WIRE -1072 528 -1072 432
FLAG -1072 528 0
SYMBOL ind2 -368 48 R0
SYMATTR InstName L1
SYMATTR Value 5.6e-3
SYMATTR Type ind
SYMATTR SpiceLine Rser=2.9
SYMBOL ind2 -368 432 M180
WINDOW 0 36 80 Left 0
WINDOW 3 36 40 Left 0
SYMATTR InstName L2
SYMATTR Value 500e-6
SYMATTR Type ind
SYMATTR SpiceLine Rser=.1
SYMBOL npn -512 192 R0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL res -592 80 R0
SYMATTR InstName R1
SYMATTR Value 100k
SYMBOL cap -464 64 R0
SYMATTR InstName C1
SYMATTR Value 10e-6
SYMATTR SpiceLine Rser=1
SYMBOL cap -592 304 R0
SYMATTR InstName C2
SYMATTR Value 1e-7
SYMBOL voltage -1072 176 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 3 24 104 Invisible 0
SYMATTR Value 5
SYMATTR InstName V1
SYMBOL pnp -928 192 M180
SYMATTR InstName Q2
SYMATTR Value 2N4403
SYMBOL voltage -976 272 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 3 24 104 Invisible 0
SYMATTR Value PULSE(5 0 0 1e-6 1e-6 .01)
SYMATTR InstName V3
SYMBOL npn -800 112 R270
SYMATTR InstName Q3
SYMATTR Value 2N3904
SYMBOL cap -768 272 R0
SYMATTR InstName C3
SYMATTR Value 7.5e-6
SYMBOL res -880 256 R0
SYMATTR InstName R2
SYMATTR Value 2e6
SYMBOL res -992 160 R0
SYMATTR InstName R3
SYMATTR Value 1000
SYMBOL res -464 320 R0
SYMATTR InstName R4
SYMATTR Value 1000
TEXT -432 184 Left 0 !K1 L1 L2 1
TEXT -1048 464 Left 0 !.tran 2.5 uic
TEXT -1048 496 Left 0 !.wave .\\bong.wav 8 10000 N008

From: Jasen Betts on 14 Jun 2010 06:22
On 2010-06-13, John Fields <jfields(a)austininstruments.com> wrote:
>
> ---
> But, since no emitter-follower cap load, no base resistor. ;)
>
> Here's the circuit, oscillating at around 675Hz.
>
> Sounds pretty good, I think, and the bong doesn't last as long as it
> used to.
>

power supply regulation (voltage at Q3 emitter) is much improved by those
changes.


--- news://freenews.netfront.net/ - complaints: news(a)netfront.net ---
From: Winfield Hill on 14 Jun 2010 07:08
John Fields wrote...
>
> Winfield Hill wrote:
>> John Fields wrote...
>>> On Fri, 11 Jun 2010 07:02:03 -0500, John Fields wrote:
>>>> On 10 Jun 2010 13:23:55 -0700, Winfield Hill wrote:
>>>>
>>>>> In a ringing bell application, as the supply voltage sags,
>>>>> and the amplitude drops, I imagine the circuit will move
>>>>> from class C back to class A operation, before stopping.
>>>>
>>>> Why imagine?
>>>>
>>>> Here's a circuit list that'll show it all _and_ it'll create
>>>> a .wav file, "bong.wav" in whatever folder the cicuit's in,
>>>> so you can hear it.
>>>>
>>>> Enjoy! :-)
>>> Oops... Here it is: [ big snip ]
>>
>> Thanks, John. I like the bong! [snip]
>---
> Sorry for the delay...
>
> Better yet, I chose a real-world inductor, included the specified
> parasitic R, and added, arbitrarily, an ohm as the ESR for the cap
> since I was too lazy to go shopping for that.

Excellent.

> Here's the circuit, oscillating at around 675Hz.
> Sounds pretty good, I think, and the bong doesn't
> last as long as it used to.

I didn't see, what did you change to lower the Q?

I had meant to suggest tying a series resistor on
Q1's emitter signal path.

John Larkin commented that the ringdown was more
due to the LC's stored energy than Q1's amplifying
role. I wonder, if you took the same LC, ignore
your new secondary, leave out Q1, etc., and you
gave it a short current spike to get it started,
what would the result look like?


--
Thanks,
- Win
From: John Fields on 14 Jun 2010 11:49
On 14 Jun 2010 04:08:08 -0700, Winfield Hill
<Winfield_member(a)newsguy.com> wrote:

>John Fields wrote...
>>
>> Winfield Hill wrote:
>>> John Fields wrote...
>>>> On Fri, 11 Jun 2010 07:02:03 -0500, John Fields wrote:
>>>>> On 10 Jun 2010 13:23:55 -0700, Winfield Hill wrote:
>>>>>
>>>>>> In a ringing bell application, as the supply voltage sags,
>>>>>> and the amplitude drops, I imagine the circuit will move
>>>>>> from class C back to class A operation, before stopping.
>>>>>
>>>>> Why imagine?
>>>>>
>>>>> Here's a circuit list that'll show it all _and_ it'll create
>>>>> a .wav file, "bong.wav" in whatever folder the cicuit's in,
>>>>> so you can hear it.
>>>>>
>>>>> Enjoy! :-)
>>>> Oops... Here it is: [ big snip ]
>>>
>>> Thanks, John. I like the bong! [snip]
>>---
>> Sorry for the delay...
>>
>> Better yet, I chose a real-world inductor, included the specified
>> parasitic R, and added, arbitrarily, an ohm as the ESR for the cap
>> since I was too lazy to go shopping for that.
>
> Excellent.
>
>> Here's the circuit, oscillating at around 675Hz.
>> Sounds pretty good, I think, and the bong doesn't
>> last as long as it used to.
>
> I didn't see, what did you change to lower the Q?

---
The wire resistance of L1 and the ESR of C1.
Right click on the components and a little dialogue will pop up which
can be edited to modify the component attributes.
---

> I had meant to suggest tying a series resistor on
> Q1's emitter signal path.

---
It does little more than attenuate the initial amplitude of the bong
and disturb its symmetry, so the rate of decay seems to be controlled
by the current C3 supplies into R2 and the base of Q3 after Q2 turns
off.

With C3 being 7.5�F and zero leakage, the range of decay varies from
1.9s with R2 open to 0.4s with R2 = 50k.
---

> John Larkin commented that the ringdown was more
> due to the LC's stored energy than Q1's amplifying
> role. I wonder, if you took the same LC, ignore
> your new secondary, leave out Q1, etc., and you
> gave it a short current spike to get it started,
> what would the result look like?


Something like this, I'd suspect:
---
Version 4
SHEET 1 936 680
WIRE -704 16 -752 16
WIRE -592 16 -624 16
WIRE -448 16 -512 16
WIRE -448 64 -448 16
WIRE -352 64 -448 64
WIRE -448 80 -448 64
WIRE -352 80 -352 64
WIRE -752 96 -752 16
WIRE -576 96 -576 64
WIRE -448 176 -448 144
WIRE -352 176 -352 160
WIRE -352 176 -448 176
WIRE -752 224 -752 176
WIRE -576 224 -576 176
WIRE -576 224 -752 224
WIRE -528 224 -528 64
WIRE -528 224 -576 224
WIRE -448 224 -448 176
WIRE -448 224 -528 224
WIRE -752 320 -752 224
FLAG -752 320 0
SYMBOL ind2 -368 64 R0
SYMATTR InstName L1
SYMATTR Value 5.6e-3
SYMATTR Type ind
SYMBOL cap -464 80 R0
SYMATTR InstName C1
SYMATTR Value 10e-6
SYMBOL voltage -752 80 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 0 -44 8 Left 0
WINDOW 3 -26 108 Left 0
SYMATTR InstName V2
SYMATTR Value 5
SYMBOL voltage -576 80 R0
WINDOW 0 -45 9 Left 0
WINDOW 3 -242 110 Invisible 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V3
SYMATTR Value PULSE(0 1 .1 1E-6 1E-6 1e-2)
SYMBOL sw -496 16 M270
WINDOW 0 32 15 Left 0
WINDOW 3 32 44 Left 0
SYMATTR InstName S1
SYMBOL res -608 0 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R1
SYMATTR Value 1
TEXT -672 256 Left 0 !.model SW SW(Ron=.01 Roff=1000Meg Vt=0.5Vh=0)
TEXT -664 288 Left 0 !.tran 1 uic

Zoom in on the current through R1 at about 1ms and you'll see smething
pretty neat. :-)

JF
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